Propeller



June 9, 1931. Q FAHLlN 1,808,888

PROPELLER Filed Dec. 28, 1929 dance 23, l dl OLE FAHIIIN, E SIOUX CITY,IOWA.

raornrnna Application filed December 28, .1929. Serial No. 417,090.

My invention relates to propellers of the all metal, removable bladevariety and has for its object to provide an improved and simplified huband blade shank construction having all the strength, durability andother requirements of a propeller for 'use in heavier than air machines.

An object or" my invention is to rovide a propeller construction inwhich t e hub 1 may be made in a single piece to provide a central hubproper and a pair of sockets to receive the blade shanks. The biggestproblem encountered in providing a remov-- able propeller bladeconstruction is that of securing the blades againstthe action ofcentrifugal force.

Another problem is that oi" balancing the blades in the hub so that thepropeller will be perfectly balanced on its axis. This problem exacts arigid re uirement that the blades shall not slip longitudinally in theirsockets.

Another desirable feature of a removable blade propeller is that theblades be adjustable about their longitudinal axis to change or adjusttheir pitch. This requires a round or at least a partially round socketand an eficient clamping device is required to secure the blade shank inits adjusted 39 position with such a socket.

My invention aims to solve all of the above problems and to embody theabove mentioned features in a propeller having a onepiece hub. The aboverequirements then create a problem in connection with the insertion andremoval of the blade shanks from their sockets. Set screws, bolts andpins are entirely inadequate for the purpose of securing the bladesagainst longitudinal 40 displacement from their sockets. The mostsatisfactory means for connecting the blade shank to its socket is theconstruction embodying coactmg devices extending ent1rely around theexterior and interior of shank 5 and socket respectively. For example,in

epression formed in of the same dimensions and material and makes itmore difiicult to properly balance the propeller.

My invention further contemplates a construction in which the bladesockets are adapted to snugly engage the entire periphcries of the bladeshanks so as to obtain a maximum gripping action against the shanks whenthe clamps are tightened.

Another object is to provide a constructionin which, if desired, only asingle slot may be provided in each blade socket to allow the necessarycontraction of the socket wall for tightening against the blade shank. Asingle slotted socket is stronger than a double slotted-socket.

Furthermore, with respect to the making. of the sockets substantiallycompletely in-= closed, a stronger construction is provided than thattype or construction which embodies a pair of widely spaced armsoccupying only a portion of the periphery of the cylindrical surfacewhich they define With these and other objects in view, my inventionconsists in the construction, arrangement and combination of the variousparts of my device, whereby the obj ectscontemplated are attained, ashereinafter more .fully set forth, pointed out in my claims,

and illustrated in the accompanying drawings, in which:

Fig. l is a combined, sectional view and. side elevation of the hub andshank assembly.

Fig. 5 is'a detail, sectional view taken on the hne 55 of Fig. 4.

I have used the reference character to indicate the hub pro er or shaftreceiving portion of the hu of my propeller. Any of the conventionaldevices for splining, keying, or otherwise securing the hub upon themotor shaft of an aeroplane may be employed and no particular means tothis end is illustrated herewith. The hub 10 and a pair of diametricallyopposed sockets 11 are formed of a single piece of metal for ed andmachined to the proper sha e an dimensions. Each socket 11 is su sstantially cylindrical in shape, providing interior cylindrical surfacesor bores adapted to snugly receive the shank 12 of a propeller blade.The interior surface of the socket might be slightly conical withoutdeparting from the spirit of my invention, although the easiest methodof machining. it is to ,mill it to a strictly cylindrical shape.

The cylindrical surface is broken only by a narrow slot or slots 13,which allow contraction of the sockets.

That portion of the socket adjacent the hub proper 10 is provided withan interior, annular recess 14. The shank 12 near its end is rovidedwith an annular recess 15. adapte to register with the recess 14.

A flexible key or a series of key elements is adapted to be insertedinto the ring shaped space formed between the two recesses 14 and 15 andthe socket wall is provided with an opening 16 to allow such insertion.One method of construction is to employ a series of parallel sidedblocks 17, connected by a wire or the like 18 to form a flexible key orchain of blocks. The opening 16 is positioned tangentially relative tothe ring shaped cavity formed by the recesses 14 and 15 and the-flexiblekey is inserted by simply pushing it through the opening.

A screw 18 is secured in the shank 12 7 within the recess 15 and flushwith or below the surface of the shank. The function of the screw 18 isto remove the key from its recess. This is accomplished by grasping thepropeller blade with the hands and twisting it in such a direction thatthe screw 18 will engage the inner end of the key. Rotation of the shankwill then force the key out of the recess. it will be understood thatanysort of projection positioned below the surface of the shank and withinthe recess 15 might be employed for this purose. p The key is of such alength as to fill the opening 16 and thus to close it against theentrance of moisture. To this end a snug fit is provided between the endblock of the key and the opening 16. In order to provide a smoothfinish, the end block may be cut with an inclined face to register withshank within the socket as wel the inclination of the surface of thesocket 11 adjacent the opening 16.

The key is held in place by a wire 20,

which is threaded through openings in a .pair of studs 19, secured inthe socket 11 on either side of the opening 16, as shown in Fi 1. Theparts will be so arranged that if y any chance the clamping mechanismfor holding the blade a ainst rotation in its socket should ,fail duringflight, the rotational pressure against the blade will cause the screw18 to move in an opposite direction whichresults in removal of the keyfrom its recess. Otherwise the pressure might be sufiicient to break thewires 20 and remove the key, whereupon the propeller blade would becomelost and result in a very serious accident to the aeroplane.

By accurately forming the blades and blade shanks and socketssymmetrically with exactly the same dimensions for each relative part,the balancing of the propeller is an easy matter. The blocks 17 willhave uniform thickness between their workin faces (the faces shown inplan in Fig. 3 and will automatically cause the blades to assumepositions exactly the same distance lflrcgm the rotational axis of the.propeller Instead of the flexible key-shown in Fig. 3, a series of steelballs 23 might be employed, being inserted by ushing them one at a timethrough the opening 16. The balls 23 will'coact with the screw 19 andscrew 18 in the same manrier' as described for the flexible key and allof the functions of the shank and the socket is transmitted between thefaces 14b, the balls 23 and the faces 15b. Since the pull is in adirection at an angle to the inclined faces 15?) and 14?), the effect ofthis ull will be to set up a series of radial forces in which the balls23 tend to force the adjacent portions of the shank and socket away fromeach other. The result is a wedging action which is distributeduniformly around the periphery of the shank actin at all points in aradial direction and thereby serving to accurately center the as totightly wedge it in place. The centering action is of importance in viewof the necessity of providing sufiicient clearance between the shank andthe socket adjacent the hub to allow the shank to enter the solid ringof ms.-

terial comprising that portion of the socket.

A slight resiliency in the outer extremities of the sockets enables themto be compressed so as to firmly grip the shanks and the same clearancemay be observed through the entire length of each socket; Thecompression of the sockets is accomplished by a pair of clamping rings30, each of which is split and provided with parallel ears 31, connectedby clamping bolts 32.

It will be understood that the slots 13 may either be provided singly orin pairs, the former having the advantage of increasing the strength ofthe sockets and the latter having the advantage of increasing theaccuracy of centering of the shanks within the sockets.

Some changes may be made in the construction and arrangement of theparts of my invention without departing from the real spirit and purposeof my invention, and it is my intention to cover by my claims anymodified forms of structure or use of mechanical equivalents, which maybe reasonably included within their scope.

I claim as my invention:

1. In an aeroplane propeller, a hub comprising a hub proper and socketsformed integrally therewith, each socket being pro-' vided with aninternal annular recess a blade shank received in the socket and formedwith an annular recess registering with the socket recess to formtherewith an annular space, the socket wall having an aperturecommunicating with said space,

means insertible through said aperture and received in said space fortransmitting longitudinal pull of the shank to the socket, and means toclamp the socket into gripping engagement with the shank. A

2. In an aeroplane propeller, a hub comprising a hub proper and socketsformed integrally therewith, each socket beingprovided with aneinternalannular recess positioned near said hub proper, a blade shank receivedin the socket and formed with an annular recess registering with thesocket recess to form therewith an annular space, the socket wall havingan aperture communicating with said space, means insertible throu h saidaperture and received in said space tor transmitting longitudinal pullof the shank to the socket, and means positioned near the end of thesocket to clamp the socket into gripping engagement with the shank.

8. In an aeroplane propeller, a hub comprising a hub proper andcylindrical sockets formed integrally therewith, each socket beingprovided with an internalannular recess, a blade shank received in andshaped to iit snugly within the socket and formed with an annular recessregistering with the socket recess to form therewith an annular space,the socket wall having an aperture communicating with said space,

nular space, the socket wall having an aperture communicating with saidspace, means insertible through said aperture and received in said spacefor transmitting longitudinal pull of the shank to the socket, and meansto secure the shank against rotation in the socket. 1

5. In an aeroplane propeller, a hub com prising a hub proper and socketsformed integrally" therewith, each socket being provided with aninternal annular recess, a blade shank received in the socket and formedwith an annular recess registering .with the socket recess to formtherewith an annular space, the socket wall having an aperturecommunicating with said space, means to secure the shank againstrotation in the socket, and means insertible throu h said aperture andreceived in said space or transmitting longitudinal pull of the shank tothe socket, said means comprising a series of shear-resisting elementsand a flexible tie member to which said elements are attached.

6. In an aeroplane propeller, a hub comprising a hub proper and socketsformed integrally therewith, each socket being provided with asubstantially unbroken cylindrical bore and with an internal annularrecess, a blade shank received in and shaped to fit snugly within thesocket and formed with an annular recess registering with the socketrecess to form therewith an annular space, the socket wall having anaperture communicating with said space, means insertible through saidaperture and received in said space for transmitting longitudinal pullof the shank to the socket, and means to clamp the socket into grippingengagement with the shank.

7. In an aeroplane propeller, a hub comprising a hub proper and socketsformed integrally therewith, each socket being pro vided with aninternal annular recess posi tioned near said hub proper, a blade shankreceived in the socket and formed with an annular recess registeringwith the socket recess to form therewith an annular space, the socketwall having an aperture coinmunicating with said space, means insertiblethrough said aperture and received in said s ace for transmittinglongitudinal ull of t e shank to the socket, the socket being gen tendedat a substantial distance beyond said space to give lateral sup ort tothe shank and means to secure the s ank against rotation in the socket.d

Signed this 23rd day of December, 1929 in the county of Woodbury andState of Iowa.

OLE FAHLIN.

